Xantrex Technology SW 2000, SW 1000, SW 600 manual Cabling Guidelines, For example

Installation
Cabling Guidelines		Table 1 : Voltage Drop Per Foot of DC Cable
Follow these guidelines and refer to Table 1 : Voltage Drop Per
			Inverter
Foot of DC Cable on page 10 to determine battery cable lengths.
			Output (W)	600	1000	1500	3000
•	Use 4 AWG copper (90 ºC insulation rating) as the smallest		Current (A)	60	100	150	300
	battery cable size. This will minimize the voltage drop between
		Wire	Resistance
	the battery and the inverter. If the cables cause an excessive	Size	(ohms/ft)		Voltage Drop per Foot
	voltage drop, the inverter may shut down when drawing higher	(AWG)	@ 25 °C
	currents because the voltage at the inverter input drops below	4	0.000253	0.0152	0.0253	0.0380	0.0759
		3	0.000201	0.0121	0.0201	0.0302	0.0603
	10.5 volts.
		2	0.000159	0.0096	0.0159	0.0239	0.0477
•	Keep all cables as short as possible, and ensure that each cable
		1	0.000126	0.0076	0.0126	0.0189	0.0378
	between the inverter and the battery is no longer than 6 feet
		0	0.000100	0.0060	0.0100	0.0150	0.0300
	(1.8 m).
		2/0	0.000079	0.0048	0.0079	0.0119	0.0237
•	Have all wires and cables terminated with correct and
		3/0	0.000063	0.0038	0.0063	0.0095	0.0189
	appropriately-sized connectors and have the connectors
		4/0	0.000050	0.0030	0.0050	0.0075	0.0150
	crimped at the place of purchase.
		Note: Xantrex recommends a size 0 cable with a maximum cable
•	Do not use aluminum. It has about 1/3 more resistance than
		length of 6 feet (1.8 m).
	copper cable of the same size, and it is difficult to make good,
		For example:
	low-resistance connections to aluminum wire.

Note: Voltage Drop per foot = Current value × Resistance value

So for a 600 W inverter output with a DC cable of size 0, multiply the maximum current of 60 A with 0.000100. The result is 0.00600 voltage drop per feet. If the cable is 6 feet long, the total voltage drop is 0.00600 × 6 ( × 2) = 0.072. (Cable length multiplied by 2.)

So for a battery operating at 12.6 V at battery terminal the voltage at the inverter terminal drops to 12.53 V.

10 Xantrex PROwatt™ SW Sine Wave Inverter Owner’s Guide